You don't need to get so offended when I post nor do you need to make in your mind that I'm trying to "common sense" you. Seriously, I couldn't care less about what you think of me personally. It only bothers me because you are so insistent about talking about me instead of the actual topic. If you care about me so much I guess you can keep talking about me, but I won't engage. As for the actual topic:
I do belief one's actual ability is directly related to one's confidence. It's going to be individualistic to some extent, of course, but the starting point is going to be their actual ability/performance. I mean, one of the main reasons I can see for sending him down is so he can play against lesser competition and as a result perform better. Chances are that you're going to be more confident going against guys that are worse. But I don't think it's always more confidence = more development. Don't get me wrong, there is some validity to it. I just don't think it's this magic bullet.
I also don't think Cody's main issue in the NBA is confidence, but instead it's that he's not an NBA caliber player atm. But even if he's not NBA level, there's an argument to be made that NBA minutes are still better. I'm weary about the GLeague as a development tool because it's a poor quality of basketball and IMO promotes bad habits. I think the confidence will come from tangible development and while I don't feel strongly about, I think having a consistent NBA role is preferred environment for that.